docs: def _get_default_value_to_cache(self, xblock):
          """
          Perform special logic to provide a field's default value for caching.
          """
          try:
              # pylint: disable=protected-access
              return self.from_json(xblock._field_data.default(xblock, self.name))
          except KeyError:
              if self._default is UNIQUE_ID:
                  return self._check_or_enforce_type(self._calculate_unique_id(xblock))
              else:
                  return self.default